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| author | Alexei Starovoitov <ast@kernel.org> | 2023-03-03 07:14:41 +0300 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-03-03 19:42:20 +0300 |
| commit | 03b77e17aeb22a5935ea20d585ca6a1f2947e62b (patch) | |
| tree | 05dc31ff00b9fb0aabb5709080a5d72eb06d0d66 /Documentation/bpf/bpf_design_QA.rst | |
| parent | 944459e88b4f5c71683b56710f96e39756afae31 (diff) | |
| download | linux-03b77e17aeb22a5935ea20d585ca6a1f2947e62b.tar.xz | |
bpf: Rename __kptr_ref -> __kptr and __kptr -> __kptr_untrusted.
__kptr meant to store PTR_UNTRUSTED kernel pointers inside bpf maps.
The concept felt useful, but didn't get much traction,
since bpf_rdonly_cast() was added soon after and bpf programs received
a simpler way to access PTR_UNTRUSTED kernel pointers
without going through restrictive __kptr usage.
Rename __kptr_ref -> __kptr and __kptr -> __kptr_untrusted to indicate
its intended usage.
The main goal of __kptr_untrusted was to read/write such pointers
directly while bpf_kptr_xchg was a mechanism to access refcnted
kernel pointers. The next patch will allow RCU protected __kptr access
with direct read. At that point __kptr_untrusted will be deprecated.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230303041446.3630-2-alexei.starovoitov@gmail.com
Diffstat (limited to 'Documentation/bpf/bpf_design_QA.rst')
| -rw-r--r-- | Documentation/bpf/bpf_design_QA.rst | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst index bfff0e7e37c2..38372a956d65 100644 --- a/Documentation/bpf/bpf_design_QA.rst +++ b/Documentation/bpf/bpf_design_QA.rst @@ -314,7 +314,7 @@ Q: What is the compatibility story for special BPF types in map values? Q: Users are allowed to embed bpf_spin_lock, bpf_timer fields in their BPF map values (when using BTF support for BPF maps). This allows to use helpers for such objects on these fields inside map values. Users are also allowed to embed -pointers to some kernel types (with __kptr and __kptr_ref BTF tags). Will the +pointers to some kernel types (with __kptr_untrusted and __kptr BTF tags). Will the kernel preserve backwards compatibility for these features? A: It depends. For bpf_spin_lock, bpf_timer: YES, for kptr and everything else: @@ -324,7 +324,7 @@ For struct types that have been added already, like bpf_spin_lock and bpf_timer, the kernel will preserve backwards compatibility, as they are part of UAPI. For kptrs, they are also part of UAPI, but only with respect to the kptr -mechanism. The types that you can use with a __kptr and __kptr_ref tagged +mechanism. The types that you can use with a __kptr_untrusted and __kptr tagged pointer in your struct are NOT part of the UAPI contract. The supported types can and will change across kernel releases. However, operations like accessing kptr fields and bpf_kptr_xchg() helper will continue to be supported across kernel |